Thermosetting resin compositions containing maleimide and/or vinyl compounds

ABSTRACT

In accordance with the present invention, there are provided novel thermosetting resin compositions which do not require solvent to provide a system having suitable viscosity for convenient handling. Invention compositions have the benefit of undergoing rapid cure. The resulting thermosets are stable to elevated temperatures, are highly flexible, have low moisture uptake and are consequently useful in a variety of applictions, e.g., in adhesive applications since they display good adhesion to both the substrate and the device attached thereto.

RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. patentapplication Ser. No. 08/300,721, filed Sep. 2, 1994, now pending, whichis hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

[0002] The present invention relates to thermosetting resin compositionsand uses therefor. In a particular aspect, the present invention relatesto thermosetting resin compositions containing maleimide resins, vinylresins, or both.

BACKGROUND OF THE INVENTION

[0003] Bismaleimides per se occupy a prominent position in the spectrumof thermosetting resins. Indeed, several is bismaleimides arecommercially available. Bismaleimide resins are used as startingmaterials for the preparation of thermoset polymers possessing a widerange of highly desirable physical properties. Depending on theparticular resin and formulation, the resins provide cured productshaving excellent storage stability, heat resistance, as well as goodadhesive, electrical and mechanical properties. Accordingly,bismaleimide resins have been used for the production of moldings,heat-resistant composite materials, high temperature coatings and forthe production of adhesive joints. Typically, however, in any particularresin formulation there is a trade-off between the various properties.For example, in the formulation of “snap” cure adhesives (i.e.,adhesives that cure in two minutes or less at ≦200° C.), it is desirableto use a system which does not require the addition of diluent tofacilitate handing. In other words, snap cure products requireformulations containing 100% reactive materials. Thus, it is desirableto prepare snap cure resins which are liquid at or about roomtemperature (i.e., low viscosity materials) for ease of handling.

[0004] Unfortunately, up until now, it has not proved possible toformulate bismaleimide compositions that are both quick curing, easy tohandle (i.e., liquid at or about room temperature), and have lowmoisture uptake. Consequently, it is a desideratum to providethermosetting bismaleimide resin compositions that produce cured resinsexhibiting a combination of highly desirable physical properties,including a combination of rapid curing and low water absorption.

[0005] A particular disadvantage of the use of bismaleimide resins forthe types of applications described above is that, at room temperature,such materials exist as solid resins which require the addition ofliquid diluents, in order for such resins to achieve a useful andprocessable viscosity. This difficulty has been compounded by the poorsolubility of bismaleimides in organic solvents. This poor solubilitygenerally necessitates the use of polar diluents, such asN-methyl-2-pyrrolidone or dimethylformamide. These diluents areundesirable, inter alia, from the viewpoint of environmental pollution.Therefore, it is another desideratum to provide bismaleimide resins thatrequire little, if any, non-reactive diluent to facilitate handling.

[0006] One approach to solving the problem of a need for a diluent hasbeen to use reactive liquid diluents. For example, the co-cure of simplebismaleimides with relatively simple divinyl ethers is known in the art.The use of such diluents is advantageous in that these materials becomeincorporated into the thermosetting resin composition, and hence do notcreate disposal problems. However, the range of suitable liquid reactivediluents is very limited. Many of the available diluents are restrictedby the low boiling points thereof, and, therefore, the high volatilitythereof; by the odor of such materials; by the toxicity of suchmaterials and/or problems with skin irritation induced thereby; by thepoor ability of such materials to solubilize bismaleimides; by the highviscosity of such materials, which, again, limits the bismaleimidesolubility and also leads to little or no tack in the formulation; bythe poor thermal stability and/or hydrolytic stability of suchmaterials; by the incompatibility of such materials with otherformulation modifiers, and the like. In particular, since the diluentsbecome an integral component of the thermosetting resin composition,they necessarily influence its properties. Consequently, it is anotherdesideratum to provide combinations of bismaleimide resins with reactivediluents which do not suffer from the above-described drawbacks and thatproduce cured resins exhibiting a combination of highly desirablephysical properties, including rapid curing and low water absorption.

[0007] Accordingly, there has existed a definite need for bismaleimideresins that produce cured resins exhibiting a combination of highlydesirable physical properties, including rapid curing and low waterabsorption. There has existed a further need for bismaleimide resinsthat require the additions of little, if any, non-reactive diluent tofacilitate handling. And there has existed a still further need forcombinations of bismaleimide resins with reactive diluents which do notsuffer from the limitations of known reactive resins and that producecured resins exhibiting a combination of highly desirable physicalproperties, including rapid curing and low water absorption. The presentinvention satisfies these and other needs and provides further relatedadvantages.

BRIEF DESCRIPTION OF THE INVENTION

[0008] In accordance with the present invention, we have developed novelthermosetting resin compositions which meet all of the above-describedneeds, i.e., produce cured resins exhibiting a combination of highlydesirable physical properties, including rapid curing and low waterabsorption, and which require little, if any, diluent to provide asystem of suitable viscosity for convenient handling. In another aspectof the invention, we have developed novel combinations of bismaleimideresins with reactive diluents, which do not suffer from the limitationsof known reactive resins and that produce cured resins exhibiting acombination of highly desirable physical properties, including rapidcuring and low water absorption. The resulting cured resins are stableat elevated temperatures, are highly flexible, have low moisture uptakeand good adhesion.

DETAILED DESCRIPTION OF THE INVENTION

[0009] In accordance with the present invention, there are providednovel maleimide resins of general formula I, as follows:

[0010] wherein:

[0011] m=1, 2 or 3,

[0012] each R is independently selected from hydrogen or lower alkyl,and

[0013] X is a monovalent or polyvalent radical selected from:

[0014] high molecular weight branched chain alkyl, alkylene or alkyleneoxide species having from about 12 to about 500 atoms in the backbonethereof,

[0015] aromatic groups having the structure:

[0016] wherein:

[0017] n=1, 2 or 3,

[0018] each Ar is a monosubstituted, disubstituted or trisubstitutedaromatic or heteroaromatic ring having in the range of 3 up to 10 carbonatoms, and

[0019] Z is a high molecular weight branched chain alkyl, alkylene oralkylene oxide species having from about 12 to about 500 atoms in thebackbone thereof,

[0020] as well as mixtures thereof.

[0021] It is a distinct advantage of the bismaleimide resins of FormulaI that they can be used with little, if any, added diluent. Generally,for easy handling and processing, the viscosity of a thermosetting resincomposition must fall in the range of about 10 to about 12,000centipoise, preferably from about 10 to about 2,000 centipoise.Maleimide resins of Formula I typically require no added diluent, orwhen diluent is used with resins contemplated by Formula I, far lessdiluent is required to facilitate handling than must be added toconventional maleimide-containing thermosetting resin systems. Preferredmaleimide resins of Formula I include stearyl maleimide, oleyl maleimideand behenyl maleimide, 1,20-bismaleimido-10,11-dioctyl-eicosane (whichlikely exists in admixture with other isomeric species produced in theene reactions employed to produce dimer acids from which thebismaleimide is prepared, as discussed in greater detail below), and thelike, as well as mixtures of any two or more thereof.

[0022] When a diluent is added, it can be any diluent which is inert tothe bismaleimide resin and in which the resin has sufficient solubilityto facilitate handling. Representative inert diluents includedimethylformamide, dimethylacetamide, N-methylpyrrolidone, toluene,xylene, methylene chloride, tetrahydrofuran, methyl ethyl ketone,monoalkyl or dialkyl ethers of ethylene glycol, polyethylene glycol,propylene glycol or polypropylene glycol, glycol ethers, and the like.

[0023] Alternatively, the diluent can be any reactive diluent which, incombination with bismaleimide resin, forms a thermosetting resincomposition. Such reactive diluents include acrylates and methacrylatesof monofunctional and polyfunctional alcohols, vinyl compounds asdescribed in greater detail herein, styrenic monomers (i.e., ethersderived from the reaction of vinyl benzyl chlorides with mono-, di-, ortrifunctional hydroxy compounds), and the like.

[0024] Now in accordance with the invention there has been found anespecially preferred class of reactive diluents corresponding to vinylor polyvinyl compounds having the general formula:

[0025] wherein:

[0026] q is 1, 2 or 3,

[0027] each R is independently as defined above,

[0028] each Q is independently selected from —O—, —O—C(O)—, —C(O)— or—C(O)—O—, and

[0029] Y is selected from:

[0030] saturated straight chain alkyl, alkylene or alkylene oxide, orbranched chain alkyl, alkylene or alkylene oxide, optionally containingsaturated cyclic moieties as substituents on said alkyl, alkylene oralkylene oxide chain or as part of the backbone of the alkyl, alkyleneor alkylene oxide chain, wherein said alkyl, alkylene or alkylene oxidespecies have at least 6 carbon atoms, preferably wherein said alkyl,alkylene or alkylene oxide species are high molecular weight branchedchain species having from about 12 to about 500 carbon atoms,

[0031] aromatic moieties having the structure:

[0032] wherein each R is independently as defined above, Ar is asdefined above, t falls in the range of 2 up to 10 and u is 1, 2 or 3,

[0033] polysiloxanes having the structure:

—(CR₂)_(m′)—[Si(R′)₂—O]_(q′)—Si(R′)₂—(CR₂)_(n′)—

[0034] wherein each R is independently defined as above, and each R′ isindependently selected from hydrogen, lower alkyl or aryl, m′ falls inthe range of 1 up to 10, n′ falls in the range of 1 up to 10, and q′falls in the range of 1 up to 50,

[0035] polyalkylene oxides having the structure:

—[(CR₂)_(r)—O—]_(q′)—(CR₂)_(s)—

[0036] wherein each R is independently as defined above, r falls in therange of 1 up to 10, s falls in the range of 1 up to 10, and q′ is asdefined above,

[0037] as well as mixtures of any two or more thereof.

[0038] Exemplary vinyl or polyvinyl compounds embraced by the abovegeneric structure include stearyl vinyl ether, behenyl vinyl ether,eicosyl vinyl ether, isoeicosyl vinyl ether, isotetracosyl vinyl ether,poly(tetrahydrofuran) divinyl ether, tetraethylene glycol divinyl ether,tris-2,4,6-(1-vinyloxybutane-4-)oxy-1,3,5-triazine,bis-1,3-(1-vinyloxybutane-4-)oxycarbonyl-benzene (alternately referredto as bis(4-vinyloxybutyl)isophthalate; available from Allied-SignalInc., Morristown, N.J., under the trade name Vectomer™ 4010), divinylethers prepared by transvinylation between lower vinyl ethers and highermolecular weight di-alcohols (e.g., α,ω-dihydroxy hydrocarbons preparedfrom dimer acids, as described above; an exemplary divinyl ether whichcan be prepared from such dimer alcohols is 10,11-dioctyleicosane-1,20-divinyl ether, which would likely exist in admixture withother isomeric species produced in ene reactions employed to producedimer acids), in the presence of a suitable palladium catalyst (see, forexample, Example 9), optionally hydrogenated α,ω-disubstitutedpolybutadienes, optionally hydrogenated α,ω-disubstituted polyisoprenes,optionally hydrogenated α,ω-distubstituted poly[(1-ethyl)-1,2-ethane],and the like. Preferred divinyl resins include stearyl vinyl ether,behenyl vinyl ether, eicosyl vinyl ether, isoeicosyl vinyl ether,poly(tetrahydrofuran) divinyl ether, divinyl ethers prepared bytransvinylation between lower vinyl ethers and higher molecular weightdi-alcohols (e.g., α,ω-dihydroxy hydrocarbons prepared from dimer acids,as described above; an exemplary divinyl ether which can be preparedfrom such dimer alcohols is 10,11-dioctyl eicosane-1,20-divinyl ether,which would likely exist in admixture with other isomeric speciesproduced in ene reactions employed to produce dimer acids), in thepresence of a suitable palladium catalyst (see, for example, Example 9),and the like.

[0039] Additionally, in accordance with another embodiment of thepresent invention, it has been found that divinyl compoundscorresponding to Formula II where —Q— is —C(O)—O— and Y is a highmolecular weight branched chain alkylene species having from about 12 toabout 500 carbon atoms are useful thermosetting resin compositions, evenin the absence of bismaleimide resins. When combined with suitableamounts of at least one free radical initiator and at least one couplingagent, these divinyl ether resins, alone, are capable of formingthermosetting resin compositions exhibiting excellent physicalproperties, including rapid cure rates and low water absorption.

[0040] In accordance with yet another embodiment of the presentinvention, there are provided thermosetting resin compositions made ofmixtures of a vinyl compound of Formula II and a maleimide correspondingto the following general formula (generally containing in the range ofabout 0.01 up to about 10 equivalents of vinyl compound per equivalentof maleimide with in the range of about 0.01 up to about 1 eq. beingpreferred where the vinyl compound is a mono- or polyvinyl ether):

[0041] wherein:

[0042] m is as defined above,

[0043] each R is independently as defined above, and

[0044] X′ is a monovalent or polyvalent radical selected from:

[0045] saturated straight chain alkyl or alkylene, or branched chainalkyl or alkylene, optionally containing saturated cyclic moieties assubstituents on said alkyl or alkylene chain or as part of the backboneof the alkyl or alkylene chain, wherein said alkyl or alkylene specieshave at least 6 carbon atoms, preferably wherein said alkyl or alkylenespecies are high molecular weight branched chain species having fromabout 12 to about 500 carbon atoms,

[0046] aromatic groups having the structure:

[0047] wherein

[0048] n is as defined above, Ar is as defined above, and Z′ is amonovalent or polyvalent radical selected from:

[0049] saturated straight chain alkyl or alkylene, or branched chainalkyl or alkylene, optionally containing saturated cyclic moieties assubstituents on said alkyl or alkylene chain or as part of the backboneof the alkyl or alkylene chain, wherein said species have at least 6carbon atoms, preferably wherein said species are high molecular weightbranched chain species having from about 12 to about 500 atoms as partof the backbone thereof,

[0050] siloxanes having the structure:

—(CR₂)_(m′)—[Si(R′)₂—O]_(q)—Si(R′)₂—(CR₂)_(n′)—

[0051] wherein each R and R′ is independently defined as above, andwherein each of m′, n′ and q is as defined above,

[0052] polyalkylene oxides having the structure:

—[(CR₂)_(r)—O—]_(q′)—(CR₂)_(s)—

[0053] wherein each R is independently as defined above, and whereineach of r, s and q′ is as defined above,

[0054] aromatic moieties having the structure:

[0055] wherein each R is independently as defined above, Ar is asdefined above, and each of t and u is as defined above,

[0056] siloxanes having the structure:

—(CR₂)_(m′)—[Si(R′)₂—O]_(q)—Si(R′)₂—(CR₂)_(n′)—

[0057] wherein each R and R′ is independently defined as above, andwherein each of m′, n′ and q′ is as defined above,

[0058] polyalkylene oxides having the structure:

—[(CR₂)_(r)—O—]_(q′)—(CR₂)_(s)—

[0059] wherein each R is independently as defined above, and whereineach of r, s and q′ is as defined above,

[0060] as well as mixtures of any two or more thereof.

[0061] Such mixtures possess a combination of highly desirable physicalproperties, including both rapid cure rates and low water absorption.

[0062] Exemplary bismaleimides embraced by Formula III includebismaleimides prepared by reaction of maleic anhydride with dimer amides(i.e., α,ω-diamino hydrocarbons prepared from dimer acids, a mixture ofmono-, di- and tri-functional oligomeric, aliphatic carboxylic acids;dimer acids are typically prepared by thermal reaction of unsaturatedfatty acids, such as oleic acid, linoleic acid, and the like, whichinduces an ene reaction, leading to the above-mentioned mixture ofcomponents). An exemplary bismaleimide which can be prepared from suchdimer amides is 1,20-bismaleimido-10,11-dioctyl-eicosane, which wouldlikely exist in admixture with other isomeric species produced in theene reactions employed to produce dimer acids. Other bismaleimidescontemplated for use in the practice of the present invention includebismaleimides prepared from α,ω-aminopropyl-terminated polydimethylsiloxanes (such as “PS510” sold by Hüls America, Piscataway, N.J.),polyoxypropylene amines (such as “D-230”, “D-400”, “D-2000” and “T-403”,sold by Texaco Chemical Company, Houston, Tex.),polytetramethyleneoxide-di-p-aminobenzoates (such as the family of suchproducts sold by Air Products, Allentown, Pa., under the trade name“Versalink” e.g., “Versalink P-650”), and the like. Preferred maleimideresins of Formula III include stearyl maleimide, oleyl maleimide,behenyl maleimide, 1,20-bismaleimido-10,11-dioctyl-eicosane (whichlikely exists in admixture with other isomeric species produced in theene reactions employed to produce dimer acids from which thebismaleimide is prepared, as discussed in greater detail elsewhere inthis specification), and the like, as well as mixtures of any two ormore thereof.

[0063] In preferred embodiments of the present invention, when mixturesof bismaleimides and divinyl compounds are employed, either X′ (of thebismaleimide) or Y (of the divinyl compound) can be aromatic, but bothX′ and Y are not both aromatic in the same formulation. Additionally, inpreferred embodiments of the present invention, when mixtures ofbismaleimides and divinyl compounds are employed, at least one of X′ orY is a high molecular weight branched chain alkylene species having fromabout 12 to about 500 carbon atoms.

[0064] Bismaleimides can be prepared employing techniques well known tothose of skill in the art. The most straightforward preparation ofmaleimide entails formation of the maleamic acid via reaction of thecorresponding primary amine with maleic anhydride, followed bydehydrative closure of the maleamic acid with acetic anhydride. A majorcomplication is that some or all of the closure is not to the maleimide,but to the isomaleimide. Essentially the isomaleimide is the dominant oreven exclusive kinetic product, whereas the desired maleimide is thethermodynamic product. Conversion of the isomaleimide to the maleimideis effectively the slow step and, particularly in the case of aliphaticamides, may require forcing conditions which can lower the yield.Nevertheless, in the case of a stable backbone such as that provided bya long, branched chain hydrocarbon (e.g.,—(CH₂)₉—CH(C₈H₁₇)—CH(C₈H₁₇)—(CH₂)₉—) the simple acetic anhydrideapproach appears to be the most cost effective method. Of course, avariety of other approaches can also be employed.

[0065] For example, dicyclohexylcarbodiimide (DCC) closes maleamic acidsmuch more readily than does acetic anhydride. With DCC, the product isexclusively isomaleimide. However, in the presence of suitableisomerizing agents, such as 1-hydroxybenzotriazole (HOBt), the productis solely the maleimide. The function of the HOBt could be to allow theclosure to proceed via the HOBt ester of the maleamic acid (formed viathe agency of DCC) which presumably closes preferentially to themaleimide. However, it is unclear why such an ester should exhibit sucha preference. In any case, it is demonstrated herein that isomidegenerated by reaction of the bismaleamic acid of 10,11-dioctyleicosanewith either acetic acid anhydride or EEDQ(2-ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline) is isomerized to thebismaleimide by catalytic amounts of HOBt.3-Hydroxy-1,2,3-benzotriazine-4-one appears to be at least as effectiveas HOBt in effecting this isomerization, whereas N-hydroxysuccinimide issubstantially less so.

[0066] Likely, isomerizing agents such as HOBt add to the isoimide toyield the amic acid ester. If this exhibits any tendency whatsoever toclose to the imide, much less a strong bias for doing so, a route forinterconverting isoimide and imide is thereby established and thethermodynamic product, imide, should ultimately prevail. Thus if theinitial closure of ester formed in the DCC reaction yields any isoimide,or if any isoimide is produced by direct closure of the acid, thesituation will be subsequently “corrected” via conversion of theisoimide to the imide by the action of the active ester alcohol as anisomerizing agent.

[0067] One problem encountered with bismaleimides is a proclivity foroligomerization. This oligomerization is the principle impediment toyield in the synthesis of bismaleimides, and may present problems inuse. Radical inhibitors can mitigate this potential problem somewhatduring the synthesis but these may be problematic in use. Fortunately,oligomer may be removed by extracting the product into pentane, hexaneor petroleum ether, in which the oligomers are essentially insoluble.

[0068] Thermosetting resin compositions of the invention also contain inthe range of 0.2 up to 3 wt % of at least one free radical initiator,based on the total weight of organic materials in the composition, i.e.,in the absence of filler. As employed herein, the term “free radicalinitiator” refers to any chemical species which, upon exposure tosufficient energy (e.g., light, heat, or the like), decomposes into twoparts which are uncharged, but which each possesses at least oneunpaired electron. Preferred as free radical initiators for use in thepractice of the present invention are compounds which decompose (i.e.,have a half life in the range of about 10 hours) at temperatures in therange of about 70 up to 180° C.

[0069] Exemplary free radical initiators contemplated for use in thepractice of the present invention include peroxides (e.g., dicumylperoxide, dibenzoyl peroxide, 2-butanone peroxide, tert-butylperbenzoate, di-tert-butyl peroxide,2,5-bis(tert-butylperoxy)-2,5-dimethylhexane, bis(tert-butylperoxyisopropyl)benzene, and tert-butyl hydroperoxide), azo compounds(e.g., 2,2′-azobis(2-methylpropanenitrile),2,2′-azobis(2-methylbutanenitrile), and1,1′-azobis(cyclohexanecarbonitrile)), and the like. Peroxide initiatorsare presently preferred because they entail no gas release upondecomposition into free radicals. Those of skill in the art recognize,however, that in certain adhesive applications, the release of gas (e.g.N₂) during cure of the adhesive would be of no real concern. Generallyin the range of about 0.2 up to 3 wt % of at least one free radicalinitiator (based on the total weight of the organic phase) will beemployed, with in the range of about 0.5 up to 1.5 wt % preferred.

[0070] Thermosetting resin compositions of the invention possess avariety of physical properties making them particularly adapted for usein the preparation of “snap” cure adhesives. Such adhesives are useful,for example, in die attach applications. When used in adhesiveapplications, it is desirable to add coupling agent(s) to theformulation.

[0071] As employed herein, the term “coupling agent” refers to chemicalspecies that are capable of bonding to a mineral surface and which alsocontain polymerizably reactive functional group(s) so as to enableinteraction with the adhesive composition. Coupling agents thusfacilitate linkage of the adhesive composition to the substrate to whichit is applied.

[0072] Exemplary coupling agents contemplated for use in the practice ofthe present invention include silicate esters, metal acrylate salts(e.g., aluminum methacrylate), titanates (e.g., titaniummethacryloxyethylacetoacetate triisopropoxide), or compounds thatcontain a copolymerizable group and a chelating ligand (e.g., phosphine,mercaptan, acetoacetate, and the like). Generally in the range of about0.1 up to 10 wt % of at least one coupling agent (based on the totalweight of the organic phase) will be employed, with in the range ofabout 0.5 up to 2 wt % preferred.

[0073] Presently preferred coupling agents contain both aco-polymerizable function (e.g., vinyl moiety, acrylate moiety,methacrylate moiety, styrene moiety, cyclopentadiene moiety, and thelike), as well as a silicate ester function. The silicate ester portionof the coupling agent is capable of condensing with metal hydroxidespresent on the mineral surface of the substrate, while theco-polymerizable function is capable of co-polymerizing with the otherreactive components of invention adhesive composition. Especiallypreferred coupling agents contemplated for use in the practice of theinvention are oligomeric silicate coupling agents such aspoly(methoxyvinylsiloxane).

[0074] In addition to the incorporation of coupling agents intoinvention adhesive compositions, it has also been found that theoptional incorporation of a few percent of the precursor bismaleamicacid greatly increases adhesion. Indeed, good adhesion is retained evenafter strenuous exposure to water.

[0075] Adhesive compositions of the invention possess a combination ofphysical properties believed to be critical to successful commercialapplication:

[0076] 1. The adhesive compositions have good handling properties,needing little, if any, inert diluent added thereto (i.e., the resincompositions form 100% reactive systems of sufficiently low viscosity);

[0077] 2. The adhesive compositions are capable of rapid (“snap”) cure,i.e., curing in two minutes or less (preferably as short as 15 seconds)at ≦200° C.;

[0078] 3. The resulting thermosets are stable to at least 250° C.,wherein “stable” is defined as less than 1% weight loss at 250° C. whensubjected to a temperature ramp of 10° C./min. in air viathermogravimetric analysis (TGA);

[0079] 4. The resulting thermosets are sufficiently flexible (e.g.,radius of curvature >1.0 meter for a 300 mil² silicone die on a copperlead frame using a cured bond line ≦2 mils) to allow use in a variety ofhigh stress applications;

[0080] 5. The resulting thermosets exhibit low-moisture uptake (innonhermetic packages); and

[0081] 6. The resulting thermosets exhibit good adhesion to substrates,even after strenuous exposure to moisture.

[0082] Adhesive compositions of the invention can be employed in thepreparation of die-attach pastes comprising in the range of about 10 upto 80 wt % of the above-described thermosetting resin composition, andin the range of about 20 up to 90 wt % filler. Fillers contemplated foruse in the practice of the present invention can be electricallyconductive and/or thermally conductive, and/or fillers which actprimarily to modify the rheology of the resulting composition. Examplesof suitable electrically conductive fillers which can be employed in thepractice of the present invention include silver, nickel, copper,aluminum, palladium, gold, graphite, metal-coated graphite (e.g.,nickel-coated graphite, silver-coated graphite, and the like), and thelike. Examples of suitable thermally conductive fillers which can beemployed in the practice of the present invention include graphite,aluminum nitride, silicon carbide, boron nitride, diamond dust, alumina,and the like. Compounds which act primarily to modify rheology includefumed silica, alumina, titania, high surface area smectite clays, andthe like.

[0083] In accordance with yet another embodiment of the presentinvention, there are provided assemblies of components adhered togetheremploying the above-described adhesive compositions and/or die attachcompositions. Thus, for example, assemblies comprising a first articlepermanently adhered to a second article by a cured aliquot of theabove-described adhesive composition are provided. Articles contemplatedfor assembly employing invention compositions include memory devices,ASIC devices, microprocessors, flash memory devices, and the like.

[0084] Also contemplated are assemblies comprising a microelectronicdevice permanently adhered to a substrate by a cured aliquot of theabove-described die attach paste. Microelectronic devices contemplatedfor use with invention die attach pastes include copper lead frames,Alloy 42 lead frames, silicon dice, gallium arsenide dice, germaniumdice, and the like.

[0085] In accordance with still another embodiment of the presentinvention, there are provided methods for adhesively attaching twocomponent parts to produce the above-described assemblies. Thus, forexample, a first article can be adhesively attached to a second article,employing a method comprising:

[0086] (a) applying the above-described adhesive composition to saidfirst article,

[0087] (b) bringing said first and second article into intimate contactto form an assembly wherein said first article and said second articleare separated only by the adhesive composition applied in step (a), andthereafter,

[0088] (c) subjecting said assembly to conditions suitable to cure saidadhesive composition.

[0089] Similarly, a microelectronic device can be adhesively attached toa substrate, employing a method comprising:

[0090] (a) applying the above-described die attach paste to saidsubstrate and/or said microelectronic device,

[0091] (b) bringing said substrate and said device into intimate contactto form an assembly wherein said substrate and said device are separatedonly by the die attach composition applied in step (a), and thereafter,

[0092] (c) subjecting said assembly to conditions suitable to cure saiddie attach composition.

[0093] Conditions suitable to cure invention die attach compositionscomprise subjecting the above-described assembly to a temperature ofless than about 200° C. for about 0.25 up to 2 minutes. This rapid,short duration heating can be accomplished in a variety of ways, e.g.,with an in-line heated rail, a belt furnace, or the like.

[0094] In accordance with a still further embodiment of the presentinvention, there is provided a method for the preparation ofbismaleimides from diamines. The invention synthetic method comprises:

[0095] adding diamine to a solution of maleic anhydride,

[0096] adding acetic anhydride to said solution once diamine addition iscomplete, and then allowing the resulting mixture to stir overnight, andthereafter treating the resulting reaction mixture with a suitableisomerizing agent.

[0097] Diamines contemplated for use in the practice of the presentinvention include saturated and unsaturated dimer diamines (such as thedimer amines sold by Henkel Corporation, Ambler, Pa., under the tradename “Versamine 552” and “Versamine 551”), α,ω-aminopropyl-terminatedpolydimethyl siloxanes (such as “PS510” sold by Hüls America,Piscataway, N.J.), polyoxypropylene amines (such as “D-230”, “D-400”,“D-2000” and “T-403”, sold by Texaco Chemical Company, Houston, Tex.),polytetramethyleneoxide-di-p-aminobenzoate (such as the family of suchproducts sold by Air Products, Allentown, Pa., under the trade name“Versalink” e.g., “Versalink P-650”), and the like. Diamine and maleicanhydride are typically combined in approximately equimolar amounts,with a slight excess of maleic anhydride preferred. Isomerizing agentscontemplated for use in the practice of the present invention include1-hydroxybenzotriazole, 3-hydroxy-1,2,3-benzotriazine-4-one,1-hydroxy-7-azabenzotriazole, N-hydroxysuccinimide, and the like.

[0098] The invention will now be described in greater detail byreference to the following non-limiting examples.

EXAMPLE 1

[0099] Preparation of the bismaleimide of hydrogenated dimer aciddiamine (Henkel Corp. Versamine 552) by closure of the bismaleamic acidwith acetic anhydride to a mixture of isomaleimide and maleimide,followed by isomerization of the isomaleimide to maleimide with1-hydroxybenzotriazole (HOBt) under mild conditions. A solution of 30.0g of Versamine 552 in 90 mL of anhydrous tetrahydrofuran (THF) wasslowly added to a solution of 12.5 g of maleic anhydride in 60 mL ofTHF. One hour after completion of the addition, 125 mL of aceticanhydride was added and the reaction mixture stirred overnight underargon atmosphere.

[0100] A Fourier transform infrared attenuated total reflectance (FTIRATR) spectrum indicated substantial conversion of the amic acid to theisoimide, with little if any amide. The reaction mixture was brought toreflux and maintained there for three hours. FTIR now indicated amixture of isoimide and maleimide with the former apparently(uncalibrated spectrum) predominating. Benzoquinone, 0.1 g, was added tothe reaction mixture and the solvent/acetic anhydride/acetic acidstripped under vacuum (ultimately 0.1 mm Hg) at 30° C. The resultingresidue was taken up in 75 mL of fresh THF and 10.2 g of HOBt (<5% H₂Omaterial) was added and dissolved in at room temperature.

[0101] An FTIR spectrum one hour after the addition indicated that theisomaleimide in the mixture had been largely, perhaps completely,consumed. Most of it appeared to have been converted to maleamic acidHOBt ester. The reaction mixture was stirred overnight. FTIR thenindicated essentially complete conversion to the maleimide.

[0102] The solvent was stripped off at 30° C. and the residue extracted2× with several hundred mL of pentane. The combined pentane fractionswere chilled in a Dry Ice/isopropyl alcohol bath, which caused a whitesolid to crystallize out. (The solid is thought to be the acetate ofHOBt, with some free HOBt). The pentane suspension was filtered cold,allowed to warm to room temperature, dried over anhydrous MgSO₄ and thesolvent stripped to give 16.9 g (43.8%) of high purity product (asdetermined by FTIR).

EXAMPLE 2

[0103] Bismaleamic acid was generated from 10.0 g of Versamine 552 and3.9 g of maleic anhydride, each in 40 mL of THF.2-Ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline (EEDQ), 9.3 g, was added.Monitoring by FTIR indicated that two days sufficed to effectessentially complete conversion to isomaleimide. HOBt, 4.9 g, wasdissolved in the reaction mixture. Monitoring by FTIR indicated that sixhours sufficed to convert all the isoimide to imide. The solvent wasstripped off and the residue extracted with pentane to yield 6.0 g ofproduct bismaleimide, contaminated with quinoline from the EEDQ.

EXAMPLE 3

[0104] E. C. Martin and A. A. DeFusco, in U.S. Statutory InventionRegistration No. H424 (Feb. 2, 1988) teach the preparation ofbismaleimide from “dimer diamine” (source not given but material NOThaving had the olefinic unsaturation removed) by means of HOBt and DCC.However, the maximum yield of bismaleimide reported is 50%. Thus,following the procedure of Martin and Fusco, the bismaleimide ofVersamine 552 (Henkel Corp.) was prepared using dicyclohexylcarbodiimide(DCC) and 1-hydroxybenzotriazole (HOBt). A solution of 50.0 g (0.179amine equiv) of Versamine 552 in 60 mL of anhydrous tetrahydrofuran(THF) was added slowly under argon atmosphere to a solution of 20.2 g(0.206 mole) of maleic anhydride in 300 mL of THF. The reaction mixturewas stirred for an hour after completion of the addition and then 25.2 g(0.186 mole) of HOBt (<5% H₂O) was dissolved in. The stirred reactionmixture was chilled in an ice bath and melted DCC added neat in portionsto a total of 49.2 g (0.238 mole). After completion of this addition,the reaction mixture was stirred in the ice bath for another hour. Theice bath was then removed and the stirred reaction mixture allowed towarm to room temperature overnight. The reaction mixture was filteredand the resulting solid was washed with THF. All THF phases werecombined, 0.2 g methoxyphenol was added and the THF stripped on a rotaryevaporator at 30° C. A thick, semisolid residue resulted. This residuewas extracted with hexane and the hexane stripped to give 40.7 g (63.3%)of a product which still had some solid impurity. This material wasextracted with pentane, which cleanly separated the solid impurity. Thepentane extract was dried over MgSO₄ and the solvent stripped to give32.1 g (49.9%) of lightly colored, low viscosity material with theexpected FTIR spectrum.

EXAMPLE 3A

[0105] The monomaleimide of oleylamine was prepared using a methodsimilar to the one described in Example 3. Oleylamine was obtained fromAldrich Chemical Company (Milwaukee, Wis.). The amine (40.0 grams, 150meqs) was dissolved in 100 ml of anhydrous THF. This solution was slowlyadded (under an argon purge) to a mechanically stirred solutioncontaining maleic anhydride (14.7 g, 150 meqs) dissolved in 100 ml ofanhydrous THF. Stirring was continued for another hour after theaddition was complete. The stirred reaction mixture was then cooled viaan external ice bath and 30.8 g (149 meqs) dicyclohexylcarbodiimide(DCC), dissolved in 30 mls anhydrous THF, was added. The chilled mixturewas stirred for an additional hour before 19.7 g (146 meqs) of1-hydroxybenzotriazole (HOBt) was added. The mixture was allowed to warmup to room temperature while stirring was continued for another sixteenhours. The reaction mixture was filtered and the filtered residue waswashed with additional THF. The combined THF solutions were stripped ona rotary evaporator at 40° C. until the pressure under full mechanicalvacuum was ≦0.5 torr. The viscous residue was then dissolved in pentane.The pentane solution was extracted five times with 50 ml portions ofaqueous methanol (70% MeOH). Magnesium sulfate was added to the washed;pentane solution fraction and it was allowed to settle overnight in arefrigerator. The solution was warmed the next morning to roomtemperature, filtered, and the solvent stripped off in a rotaryevaporator (using water aspirator, followed by full mechanical vacuumuntil the pressure remained ≦0.5 torr for one hour). The productrecovered was a light brown, low viscosity liquid with an FTIR spectrumconsistent with what one would predict for the expected structure.

EXAMPLE 3B

[0106] A diacrylate was prepared as follows from the dimer diol derivedfrom oleic acid. This diol was obtained from Unichema North America(Chicago, Ill.) under the designation Pripol 2033. Approximately 53.8grams of Pripol 2033 and 22.3 grams of triethylamine (reagent grade fromAldrich Chemical Co., Milwaukee, Wis.) were dissolved in 136.0 grams ofdry acetone. This solution was chilled to 5° C. in an ice bath while thecontents of the flask were blanketed under a slow argon purge. Thesolution was subjected to mechanical stirring while acroyl chloride(18.1 grams dissolved in 107.3 grams of dry acetone) was added dropwiseover a two hour period. Stirring was continued for another hour and thebath was allowed to warm up to room temperature. Approximately 7.1 mg ofmethoxy hydroquinone (inhibitor) was added to the final reaction productand the acetone was removed on a rotary evaporator. The product was thendissolved in methylene chloride and this solution was then extractedthree times with 7% aqueous sodium bicarbonate and another two timeswith 18 meg-ohm water. The solution was dried over magnesium sulfate andthen filtered. Finally, the methylene chloride solvent was removed underfull mechanical vacuum on the rotary evaporator. An FTIR analysis ofthis product showed a characteristic ester absorption around 1727 wavenumbers. The final yield was 71% (based on the starting Pripol 2033).

EXAMPLE 4

[0107] This example illustrates improvement in yield obtained by using3-hydroxy-1,2,3-benzotriazin-4-one (HOBtCO) instead of HOBt. Thebismaleamic acid of Versamine 552 was prepared by the dropwise additionover an hour (dry argon atmosphere) of a solution of 144.0 g ofVersamine 552 in 100 mL of dry dichloromethane (CH₂Cl₂) to a stirredsolution of 50.4 g maleic anhydride in 300 mL of dry CH₂Cl₂ chilled inan ice bath. The ice bath was removed at the end of the addition and thereaction mixture stirred for another hour. The ice bath was then putback in place and 84.0 g (100%) of 3-hydroxy-1,2,3-benzotriazin-4-onewas added. To the chilled reaction mixture was then added a solution of106.1 g of DCC in 100 mL of CH₂Cl₂ over 30 minutes, with stirring. Aftercompletion of the addition, the ice bath was removed and the reactionmixture stirred overnight at room temperature. The reaction mixture wassuction-filtered and the collected solid was washed twice with 100 mLportions of CH₂Cl₂, which were combined with the original CH₂Cl₂filtrate. The CH₂Cl₂ was stripped on a rotary evaporator, at 35-40° C.,ultimately under oil-pump vacuum (0.1 Torr). The resulting residue wasextracted twice with 500 mL portions of pentane and once with a 1000 mLportion of pentane, all of which were combined and stripped on therotary evaporator. The original residue was extracted with more pentanefor a final total of four liters of pentane. After condensation to avolume of 500 mL, the solution was stored in the freezer overnight. Itwas allowed to warm to room temperature, suction-filtered through finefilter paper and the remaining pentane stripped to yield 145.0 g (80.0%)of the bismaleimide.

EXAMPLE 5

[0108] This example demonstrates that a very satisfactory yield may beobtained using much less than an equivalent of the coreactant compound,3-hydroxy-1,2,3-benzotriazin-4-one (HOBtCO), and that it may be addedafter the DCC. The bismaleamic acid of Versamine 552 was generated as inExample 4 from 136.5 g of Versamine 552 and 46.3 g of maleic anhydride,except that the solvent was THF rather than CH₂Cl₂. To the chilled (icebath) reaction mixture was added a THF solution of DCC containing 100.5g of DCC. After an FTIR spectrum showed that the amic acid had beenentirely converted to isoimide, 12 g (15%) of HOBtCO was added and thereaction mixture maintained at 45° C. for four hours, which sufficed, byFTIR, to convert the isoimide entirely to imide. Workup as in thepreceding example resulted in a yield of 122 g (70%) of thebismaleimide.

EXAMPLE 6

[0109] This example illustrates the use of1-hydroxy-7-aza-1,2-3-benzotriazole (HOAt) as the coreactant compound,again at a low level. Using the procedure described in the precedingexample but with 20% HOAt, 51.5 g of Versamine 552 yielded 48.8 g(70.0%) of the BMI. Separation of the HOAt from the reaction product wasfacile and 4.4 g was recovered.

EXAMPLE 7

[0110] The following experiments demonstrate improvements in the yield,obtained by the procedure of Martin and Fusco by changes in procedureand protocol while still using HOBt. The procedure and protocol used isthat detailed in Example 4 in which 3-hydroxy-1,2,3-benzotriazin-4-oneis used except that the reaction solvent was THF in all cases hererather than the dichloromethane used in Example 4. A reaction using 100%HOBt gave a yield of 51.9%; four reactions using 80% HOBt gave yields of56.8, 60.0, 65.1 and 70.2%, respectively. Also, a reaction employingdimer diamine in which the olefinic unsaturation has not been removed,as in U.S. Statutory Invention Registration No. H424 (Henkel Versamine551 rather than 552), and 80% HOBt gave a yield of 52.2% of thecorresponding BMI.

[0111] Examples 4-7 show that by variations in solvent and procedures,yields as high as 70% may be obtained using HOBt and as high as 80%using 3-hydroxy-1,2,3-benzotriazin-4-one (HOBtCO) in lieu of HOBt. Alsothe realization in the course of the present work that compounds such asHOBt and HOBtCO are potent agents for the isoimide to imideisomerization means that the reaction may be run with less than a fullequivalent of such. The fact that such compounds are first consumed andthen liberated during the cyclodehydration, and are thus in principlecatalysts, does not of itself necessarily imply that they may be used atless than a full equivalent since the potentially competing reaction ofdirect cyclodehydration of the amic acid by DCC to the isoimide wouldstill be of concern. However, as it turns out, HOBt, HOBtCO, and thelike are effective at promoting the facile isomerization which leads tothe desired product.

EXAMPLE 8

[0112] A masterbatch of the bisisomaleimide of Versamine 552 wasprepared from 30.0 g of the amine, dissolved in 80 mL of anhydrous THFand added dropwise to a solution of 11.7 g of maleic anhydride in 100 mLof anhydrous THF to yield the bismaleamic acid, followed by the additionof 125 mL of neat acetic anhydride. One half of this reaction mixturewas allowed to stand for three days at room temperature. The solvent andexcess acetic anhydride were stripped to leave the isomaleimide.Portions of this isomaleimide were treated as follows. A 5.0 g samplewas dissolved in anhydrous THF along with 2.6 g of3-hydroxy-1,2,3-benzotriazin-4-one (HOBtCO). This solution was allowedto stand overnight, which sufficed to effect complete conversion to themaleimide, ultimately recovered in 56% yield. Another 5.0 g of theisomaleimide was treated with 2.3 g of HOBt in the same manner; a 46%yield of bismaleimide was recovered as well as a larger amount ofoligomerized material than in the HBtCO reaction. A third portion of theisomaleimide, 4.9 g, was treated with 2.1 g of N-hydroxysuccinimide inacetonitrile solution. In this case, overnight reflux was used to effectconversion to the maleimide, recovered in only 36% yield.

EXAMPLE 9

[0113] A divinyl ether was prepared as follows from the dimer diolderived from oleic acid employing Pripol 2033 dimer diol obtained fromUnichema North America (Chicago, Ill.), vinyl propyl ether obtained fromBASF Corp. (Parsippany, N.J.), and palladium 1,10-phenanthrolinediacetate [Pd(phen)(OAc)₂]. Thus, the Pripol was pre-dried overmolecular sieves (3A) approximately 3 hours prior to use. Next, to aclean and dry 1 liter flask, with large oval Teflon stir bar, was added149.1 grams (523.3 meqs) of Pripol 2033, 280 grams (3256 meqs) of vinylpropyl ether, and 1.0 grams Pd(phen) (AcO)₂ (2.5 meqs). The head spaceof the flask was purged with argon and the reaction flask fitted with anoil bubbler (to eliminate any pressure build up in the flask). The flaskwas placed on a magnetic stir plate and stirring initiated and continuedfor approximately 48 hours. The solution color changed from a lightyellow to a deep dark brown. After 48 hours, an aliquot was removed andthe bulk of the vinyl propyl ether was blown off using argon. An FTIRanalysis was performed on the residue and it was determined thatvirtually all the alcohol had reacted (i.e., no OH absorbance between3400 and 3500 cm⁻¹ remained).

[0114] To the original solution approximately 10-15 grams of activatedcharcoal was added. The solution was mixed for approximately 1 hour onthe magnetic stir plate, then about 5 grams of Celite was added. Theactivated charcoal and Celite were removed via suction filtrationthrough a fritted funnel packed with additional Celite (about anadditional 15 grams). The solution that passed through the funnelretained a slight brown color.

[0115] The bulk of the excess vinyl propyl ether was then removed usinga rotary evaporator at a bath temperature of 35-40° C. under a partial(water aspirator) vacuum. Once condensation stopped, the cold traps wereemptied and replaced. A full mechanical vacuum was then applied andcontinued at the 35-40° C. bath temperature for approximately 1 hour.The vacuum decreased to under 1.0 torr within an hour. Product recoveredat this point was a light brown, low viscosity liquid.

[0116] The last traces of propyl vinyl ether were removed using afalling film molecular still (operated at a strip temperature of 70° C.and a vacuum of less than one torr). The product residence time in thestill head was about 15 to 20 minutes and the complete strippingprocedure required about two hours. The product, following this strip,had no residual odor characteristic of the vinyl propyl ether.Thermogravimetric analysis showed no significant weight loss by 200° C.The product, therefore, was considered to be free of the vinyl etherstarting material and any propyl alcohol co-product.

EXAMPLE 9A

[0117] A divinyl ether was prepared from an alpha-omega terminated,hydrogenated 1,2-polybutadiene. This diol had a molecular weight ofapproximately 3,000 grams per mole and was obtained from Ken SeikaCorporation (Little Silver, N.J.) under the trade name GI-3000. Themethod used to synthesize the divinyl ether was analogous to the onedescribed in Example 9. Approximately 51.5 grams (34.4 meqs) of GI-3000was dissolved in 158.9 grams (1,840 meqs) of vinyl propyl ether. Themixture was stirred magnetically until a homogeneous solution wasobtained. Palladium 1,10-phenanthroline diacetate (0.53 grams, 1.33meqs) was then added and the entire mixture was allowed to stir for fivedays at room temperature under an argon atmosphere. An aliquot of thereaction product was removed and the volatiles (vinyl propyl ether andpropanol) were blown off. An FTIR trace obtained on this residuedemonstrated that the diol had been completely converted to thecorresponding divinyl ether.

[0118] The bulk of the reaction product was then worked up according tothe procedure described in the Example 9. The solution was decolorizedusing activated charcoal, treated with Celite, and the suspension wasthen passed through a filter packed with additional Celite. The bulk ofthe excess vinyl propyl ether and propanol were removed using a rotaryevaporator (bath temperature ≦40° C.) at full mechanical pump vacuum.Evaporation was continued until the pressure fell to under one torr. Thelast traces of volatiles were stripped off using a falling filmmolecular still as described in Example 9. The final product was aviscous (although less so than the starting diol) straw colored liquid.

EXAMPLE 9B

[0119] Another oligomer diol was subjected to transvinylation. Thealpha-omega diol of hydrogenated polyisoprene was employed for thisexample, and is available from Ken Seika Corporation under thedesignation “TH-21”. This oligomer has an approximate molecular weightof 2,600 grams per mole. The same method as described in Example 9 wasused to convert this diol to the corresponding divinyl ether. Thus,TH-21 (52.0 grams, 40 meqs) was dissolved in 83.7 grams of vinyl propylether (972 meqs) and 0.4 grams (1.0 meq) of palladium1,10-phenanthroline diacetate catalyst was added. The mixture wasstirred magnetically at room temperature under an argon atmosphere forsix days. An evaporated aliquot of the reaction mixture was found to beessentially free of alcohol functionality according to FTIR analysis.The bulk of the reaction product was worked up as per the methoddescribed in Example 9. The final product was an amber, viscous liquid(again the viscosity of the divinyl compound was considerably lower inviscosity than the starting diol).

EXAMPLE 9C

[0120] Iso-eicosyl alcohol, obtained from M. Michel and Co., Inc. (NewYork, N.Y.) was transvinylated according to the method described inExample 9. The alcohol (100.3 grams. 336 meqs) was dissolved in 377.4grams of the vinyl propyl ester (4,383 meqs) and 1.0 gram (2.5 meqs) ofpalladium 1,10-phenanthroline diacetate catalyst was added. The mixturewas magnetically stirred under an argon atmosphere for four days. AnFTIR trace of the evaporated reaction product showed that no detectablealcohol residue remained. The product was worked up as previouslydescribed. The final material was a pale yellow liquid with a“water-like” viscosity.

EXAMPLE 9D

[0121] Behenyl alcohol (1-docosanol), obtained from M. Michel and Co.,Inc. (New York, N.Y.) was transvinylated substantially as described inExample 9, however, since the starting alcohol was a waxy solid withlimited room temperature solubility in vinyl propyl ether, it wasnecessary to conduct the reaction at an elevated temperature. Thus, amixture of the alcohol (100.8 grams, 309 meqs), vinyl propyl ether(406.0 grams, 4,714 meqs), and palladium 1,10-phenanthroline diacetatecatalyst (1.0 gram, 2.5 meqs) was magnetically stirred at 50° C. underan argon atmosphere for 20 hours. Analysis of an evaporated aliquotafter this period showed that no detectable alcohol remained. Thebehenyl vinyl ether was worked up as described above. The final productwas an off-white waxy solid.

EXAMPLE 10

[0122] An organic adhesive vehicle was prepared using 2.78 grams (1.0equivalents) of the BMI prepared according to Example 8, 0.94 grams (0.5equivalents) of the divinyl ether prepared according to Example 9, and0.58 grams (0.5 equivalents) of Vectomer 4010 (i.e.,bis(4-vinyloxybutyl) isophthalate). An additional 1% by weight dicumylperoxide (initiator), 0.5% gamma-methacryloxypropyltrimethoxysilane(coupling agent), and 0.5%beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (coupling agent) wereadded to complete the organic adhesive mix.

[0123] Twenty-two percent by weight of the organic adhesive mixture wasadded to 78% by weight of silver metal filler. The mixture was stirredunder high shear until homogeneous. The resulting paste was thendegassed at 1 torr. The paste was dispensed onto silver plated copperlead frames using a starfish dispense nozzle. Bare silicon dice (300×300mils on a side) were then placed on top and compressed into the adhesiveuntil a 2.0 mil bondline had been attained (this process is virtuallyinstantaneous when using automated “pick and place” equipment. Theassembled parts were then cured on a heated surface (hot plate)controlled at 200° C. for two minutes. Additional void test parts (whichwere assembled in parallel using a 300×300 glass slide to replace thesilicon die) showed the cured adhesive film to be free of voiding. Halfof the assembled parts were subjected to tensile test immediately. Theother half were placed in a pressure cooker at 121° C. for 168 hours(i.e., one week). The pressure cooker is considered to be a veryaggressive test that has predictive value for the long term robustnessof adhesives used in non-hermetic environments.

[0124] Adhesion strength testing was performed on these parts using a“Tinius Olsen 10,000” tensile test machine. Steel cube studs(0.25×0.25×0.8 inches) were attached at room temperature to the top ofthe die and the bottom of the lead frame using Loctite 415 cyanoacrylateglue. The cubes were attached using a V-block fixturing device to assuretheir co-linearity. Once the room temperature gluing operation wascomplete (˜one hour later), the entire assembly was loaded into thetensile test machine. Pins were used to secure the steel blocks (throughholes present in each of the test blocks) to the upper and lower arms ofthe stud pull machine. The tensile pull speed used was 3.00 inches perminute, and the adhesion measurement was recorded in terms of pounds offorce. The tensile test results for the initial and post pressure cookerparts are presented in Table 1. TABLE 1 Initial Adhesion (lbs) RetainedAdhesion (lbs) 191 141 169 147 179 112 180 153 166 126 155 138 174 161175 121 111 133 149 149 164 154 144 119

[0125] As the results in Table 1 demonstrate, the product was found tohave good initial and retained adhesion. The average adhesion for theparts prior to pressure cooker treatment was 163 pounds and afterpressure cooker it was 138 pounds. Thus, even after one full week at twoatmospheres pressure of steam (14.7 psig, 121° C.) about 85% of theinitial adhesion was retained. It is noteworthy that a competitivematerial which was run at the same time had an initial adhesion of 338pounds, but dropped down to zero after the pressure cooker treatment.

EXAMPLE 10A

[0126] A composition was formulated using a monovinyl ether diluent anda divinyl ether “rubber” comonomer. The addition of these materials wasused to enhance certain properties of the adhesive composition.Specifically, the monovinyl ether was used to reduce the viscosity andincrease the thixotropic index (defined as the quotient of the 1 rpmover the 20 rpm viscosity). The “rubber” comonomer was used to“flexibilize” the cured adhesive. Flexibility is especially importantwhen thin bondlines are used since stress increases as bondlinedecreases. A convenient measure of stress for a cured part is the radiusof curvature (ROC). This measurement is traditionally done with asurface profilometer and is an index of the “bowing” of the silicon die.The higher the ROC (i.e., the larger the sphere described by measuredarc) the lower the stress. It is generally desirable to have an ROC ≧onemeter. The composition described in Example 10 results in a radius ofcurvature of greater than 1.5 meters when used at a 2.0 mil bondline,but gives a ROC of less than one meter when the bondline is reduced to1.0 mils.

[0127] The monovinyl ether diluent used, vinyl octadecyl ether, waspurchased from BASF Corp. (Parsippany, N.J.). The divinyl ether “rubber”was the product described in Example 9B. An organic adhesive vehicle wasprepared using 1.29 grams (3.7 meqs) of the BMI prepared according toExample 8, 0.1125 grams (0.38 meqs) vinyl octadecyl ether, and 0.1127grams (0.08 meqs) of the divinyl ether prepared according to Example 9B.An additional 1.0% by weight dicumyl peroxide (initiator) and 2.7%gamma-methacryloxy-propyltrimethoxysilane coupling agent were added tocomplete the organic adhesive mix.

[0128] Twenty-seven percent by weight of the above organic adhesivemixture was added to 73% by weight of silver filler. The mixture washomogenized under high shear and then degassed using a full mechanicalpump vacuum. The adhesive was dispensed into silver plated copper leadframes using a starfish dispense nozzle. Bare silicon dice (300×300 milon a side) were placed on top and compressed into the adhesive toachieve a 1.0 mil bondline. A similar set of parts was generated usingthe adhesive composition described in Example 10. The parts were curedfor one minute at 200° C. The radius of curvature for parts using theadhesive described here was 1.29 meters. The ROC for the control partswas 0.76 meters. The 10 rpm viscosity (Brookfield viscometer) for theadhesive described here was 5,734 centipoise at 25.0° C. and thethixotropic index was 6.60. The control adhesive had a 12,040 10 rpmviscosity at 25.0° C. and a thixotropic index of 4.97. The post cureadhesion results for the adhesive described here and the control were asfollows: TABLE 2 Adhesion for Test Paste Adhesion for Control (lbs)(lbs) 157  72 149 139 154 175 134 149 158  97 159 136

[0129] The results presented here demonstrate that several of theadhesive composition properties can be improved with little or nosacrifice of initial adhesion by the incorporation of modest amounts ofa reactive diluent and a flexibilizing comonomer.

EXAMPLE 10B

[0130] The previous examples demonstrated how adhesive compositionscould be formulated in which no more than one equivalent of vinyl ethercomonomer is used in conjunction with an excess of a bismaleimide. It isnot necessary to have any vinyl ether present in the composition,however. That is to say, that compositions may be formulated wheremaleimide is the only polymerizable function.

[0131] Thus, an organic adhesive vehicle was prepared using 96.25% byweight of the BMI prepared according to Example 8, 1% by weight USP90MD[1,1 bis(t-amyl peroxy) cyclohexane—an initiator available from WitcoCorporation, Marshall, Tex.], 0.76%gamma-methacryloxypropyltrimethoxysilane (coupling agent), and 1.72%beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (coupling agent).

[0132] Twenty-five percent by weight of the above organic adhesivemixture was added to 75% by weight of silver metal filler. The mixturewas sheared and degassed as before. Dispense and die placement wereperformed as described earlier (300×300 mil silicon die on Ag coated Culead frames). The bondline used was 1.0 mils and the cure time was oneminute at 200° C. Initial and post pressure cooker (16 hour) adhesionvalues are presented in the following table. TABLE 3 Initial AdhesionPost Pressure Cooker Adhesion (lbs) (lbs) 165  83 137 188 115 143 171122 148 208 154 200

[0133] This composition exhibited a narrow exotherm with a maxima at128.8° C. via differential scanning calorimetry (DSC) and a weight lossof less than 0.75% by 350° C. according to TGA (10° C./min. using an airpurge). This composition therefore demonstrates the viability of an “allmaleimide” snap cure adhesive system.

EXAMPLE 10C

[0134] The previous examples have demonstrated the utility ofmaleimide/vinyl ether co-cure and maleimide homocure for use asadhesives. Other polymerizable functional groups including acrylate andmethacrylate may also be used alone or in combination with maleimideand/or vinyl ether monomers.

[0135] Thus, an organic adhesive vehicle was prepared using 4.00 gramsof the diacrylate prepared according to Example 3B, 1.00 gramdecanendiol dimethacrylate (purchased from Polysciences, Inc.,Warrington, Pa.), and 1.00 gram Ricon R-130 Epoxy (obtained fromAdvanced Resins, Inc., Grand Junction, Colo.). Two percent by weight ofdicumyl peroxide initiator was dissolved in this mix.

[0136] Twenty percent by weight of the organic adhesive mixture wasadded to 80% by weight silver metal filler. The mixture was homogenizedusing high shear and then degassed. Parts were assembled as before using300×300 silicon on Ag plated Cu lead frames. The cure condition was 200°C. for one minute, and the bondline thickness used was 1.0 mil. Theinitial adhesion values an the corresponding failure mode information ispresented in the following table: TABLE 4 Initial Adhesion (lbs) FailureMode (lbs) 66 material 55 material 67 material 62 material 63 material59 material

[0137] The measured adhesion for this mixture was lower than observedfor most of the BMI containing compositions. The failure mode, however,was of the most preferred (all material) type (i.e., entirely cohesiverather than adhesive failure). The radius of curvature for the curedadhesive at the bondline thickness used here was 2.51 meters.

EXAMPLE 11

[0138] A test paste was made that contained one equivalent each of thebismaleimide of Versalink 650(polytetramethyleneoxide-di-p-aminobenzoate, marketed by Air Products,Allentown, Pa.) and the divinyl ether of tetraethylene glycol. Theorganic phase had 1% by weight of dicumyl peroxide. Seventy-five percentby weight silver filler was used in the paste. Ten parts were assembledand cured as per the preceding example using this paste that containedno coupling agent. One percent by weight of the same mixed couplingagents noted above were then added to the paste. Another ten parts wereassembled and cured using this new paste mix. Both groups of parts werethen divided into two sets. Half of the parts from each group was testedfor tensile strength immediately and the other half following four hoursof immersion in the pressure cooker. Tensile strength measurements wereperformed according to the procedure described in Example 10. Theresults of this testing are summarized in Table 5. TABLE 5 TensileStrength of Adhesive Bond No Coupling With Coupling Agent Agent InitialValue Post Moisture Initial Value Post Moisture 110.7 0 112.3 88.8 111.20 102.6 84.3 107.7 0 108.5 83.8 110.5 0 109.2 87.9 106.5 0 115.6 93.3

[0139] The data in Table 5 shows that the presence of the couplingagents has a dramatic impact on the survival of the adhesive bond inextreme moisture environments.

EXAMPLE 12

[0140] A test was conducted to test the adhesion performance ofinvention compositions following a one minute cure at 200° C. Thebondline used for these parts was also dropped from 2.0 down to 1.0 milsduring the attach step. Stress, which is induced by the large thermalmismatch between the silicon and lead frame, increases when the bondlineis decreased. The organic adhesive portion of paste consisted of oneequivalent each of the BMI prepared according to Example 8, and Vectomer4010 (i.e., bis(4-vinyloxybutyl)isophthalate). It also contained 4.5% ofgamma-methacryloxypropyl-trimethoxysilane coupling agent, as well as0.95% dicumyl peroxide initiator. A paste was made consisting of 22% byweight of this adhesive composition and 78% by weight of silver flake.The paste was degassed and then used to attach 300×300 mil silicon dieto silver plated copper lead frames using the reduced bondline and curetime. Six parts were assembled and cured. Two void test parts (sameconditions but using 300×300 mil glass slides to replace the silicondie) were also made. There was no evidence of porosity in the void testparts. Tensile strength measurements were performed according to theprocedure described in Example 10. The tensile test values for the otherparts were: 116, 114, 119; 122, 128 and 134 pounds force.

[0141] While the invention has been described in detail with referenceto certain preferred embodiments thereof, it will be understood thatmodifications and variations are within the spirit and scope of thatwhich is described and claimed.

That which is claimed is:
 1. A bismaleimide composition having thestructure:

wherein: m=1, 2 or 3, each R is independently selected from hydrogen orlower alkyl, and X is a monovalent or polyvalent radical selected from:branched chain alkyl, alkylene or alkylene oxide species having fromabout 12 to about 500 carbon atoms, aromatic groups having thestructure:

wherein: n=1, 2 or 3, each Ar is a monosubstituted, disubstituted ortrisubstituted aromatic or heteroaromatic ring having in the range of 3up to 10 carbon atoms, and Z is a branched chain alkyl, alkylene oralkylene oxide species having from about 12 to about 500 atoms in thebackbone thereof, or mixtures thereof.
 2. A thermosetting resincomposition comprising: (a) a maleimide composition having thestructure:

wherein: m=1, 2 or 3, each R is independently selected from hydrogen orlower alkyl, and X is a monovalent or polyvalent radical selected from:branched chain alkyl, alkylene or alkylene oxide species having fromabout 12 to about 500 carbon atoms, aromatic groups having thestructure:

wherein: n=1, 2 or 3, each Ar is a monosubstituted, disubstituted ortrisubstituted aromatic or heteroaromatic ring having in the range of 3up to 10 carbon atoms, and Z is a branched chain alkyl, alkylene oralkylene oxide species having from about 12 to about 500 atoms in thebackbone thereof, or mixtures thereof; (b) in the range of 0.2 up to 3wt % of at least one free radical initiator, based on the total weightof the composition; and (c) optionally, a diluent for the bismaleimidecomposition.
 3. The thermosetting resin composition according to claim2, further comprising (d) in the range of 0.1 up to 10 wt % of at leastone coupling agent, based on the total weight of the composition.
 4. Thethermosetting resin composition according to claim 3, wherein thecomposition has a viscosity of from about 10 to about 12,000 centipoise.5. The thermosetting resin composition according to claim 3, wherein thecomposition has a viscosity of from about 10 to about 2,000 centipoise.6. The thermosetting resin composition according to claim 3, wherein thediluent is selected from dimethylformamide, dimethylacetamide,N-methylpyrrolidone, toluene, xylene, methylene chloride,tetrahydrofuran, glycol ethers, methyl ethyl ketone or monoalkyl ordialkyl ethers of ethylene glycol, polyethylene glycol, propylene glycolor polypropylene glycol.
 7. The thermosetting resin compositionaccording to claim 3, wherein the free radical initiator is selectedfrom peroxides or azo compounds.
 8. The thermosetting resin compositionaccording to claim 3, wherein the coupling agent is selected fromsilicate esters, metal acrylate salts, titanates or compounds containinga co-polymerizable group and a chelating ligand.
 9. A thermosettingresin composition comprising: (a) a maleimide having the structure:

wherein: m=1, 2 or 3, each R is independently selected from hydrogen orlower alkyl, and X′ is selected from: saturated straight chain alkyl,alkylene or alkylene oxide, or branched chain alkyl, alkylene oralkylene oxide, optionally containing saturated cyclic moieties assubstituents on said alkyl, alkylene or alkylene oxide chain or as partof the backbone of the alkyl, alkylene or alkylene oxide chain, whereinsaid species have at least 6 carbon atoms, aromatic groups having thestructure:

wherein n=1, 2 or 3, each Ar is a monosubstituted, disubstituted ortrisubstituted aromatic or heteroaromatic ring having in the range of 3up to 10 carbon atoms, and Z′ is selected from: saturated straight chainalkyl, alkylene or alkylene oxide, or branched chain alkyl, alkylene oralkylene oxide, optionally containing saturated cyclic moieties assubstituents on said alkyl, alkylene or alkylene oxide chain or as partof the backbone of the alkyl, alkylene or alkylene oxide chain, whereinsaid species have at least 6 carbon atoms, siloxanes having thestructure: —(CR₂)_(m′)—[Si(R′)₂—O]_(q′)—Si(R′)₂—(CR₂)_(n′)— wherein eachR is independently defined as above, and each R′ is independentlyselected from hydrogen, lower alkyl or aryl, m′ falls in the range of 1up to 10, n′ falls in the range of 1 up to 10, and q′ falls in the rangeof 1 up to 50, polyalkylene oxides having the structure:—[(CR₂)_(r)—O—]_(q′)—(CR₂)_(s)— wherein each R is independently asdefined above, r falls in the range of 1 up to 10, s falls in the rangeof 1 up to 10, and q′ is as defined above, aromatic moieties having thestructure:

wherein each R is independently as defined above, t falls in the rangeof 2 up to 10, u is 1, 2 or 3, and Ar is as defined above, polysiloxaneshaving the structure: —(CR₂)_(m′)—[Si(R′)₂—O]_(q)—Si(R′)₂—(CR₂)_(n′)—wherein each R and R′ is independently defined as above, and whereineach of m′, n′ and q is as defined above, polyalkylene oxides having thestructure: —[(CR₂)_(r)—O—]_(q′)—(CR₂)_(s)— wherein each R isindependently as defined above, and wherein each of r, s and q′ is asdefined above, as well as mixtures of any two or more thereof, (b) inthe range of about 0.01 up to about 10 equivalents of a vinyl compoundper equivalent of maleimide, wherein said vinyl compound has thestructure:

wherein: q is 1, 2 or 3, each R is independently as defined above, eachQ is independently selected from —O—, —O—C(O)—, —C(O)— or —C(O)—O—, andY is selected from: saturated straight chain alkyl, alkylene or alkyleneoxide, or branched chain alkyl, alkylene or alkylene oxide, optionallycontaining saturated cyclic moieties as substituents on said alkyl,alkylene or alkylene oxide chain or as part of the backbone of thealkyl, alkylene or alkylene oxide chain, wherein said species have atleast 6 carbon atoms, aromatic moieties having the structure:

wherein each R is independently as defined above, and each of Ar, t andu is as defined above, siloxanes having the structure:—(CR₂)_(m′)—[Si(R′)₂—O]_(q)—Si(R′)₂—(CR₂)_(n′)— wherein each R and R′ isindependently defined as above, and wherein each of m′, n′ and q is asdefined above, polyalkylene oxides having the structure:—[(CR₂)_(r)—O—]_(q′)—(CR₂)_(s)— wherein each R is independently asdefined above, and wherein each of r, s and q′ is as defined above, aswell as mixtures of any two or more thereof, (c) in the range of 0.2 upto 3 wt % of at least one free radical initiator, based on the totalweight of the composition.
 10. A thermosetting resin compositionaccording to claim 9 further comprising (d) in the range of 0.1 up to 10wt % of at least one coupling agent, based on the total weight of thecomposition.
 11. A thermosetting resin composition according to claim 10wherein X′ is a polyvalent radical selected from: branched chainalkylene species having from about 12 to about 500 carbon atoms,aromatic groups having the structure:

wherein n=1, 2 or 3, each Ar is a monosubstituted, disubstituted ortrisubstituted aromatic or heteroaromatic ring having in the range of 3up to 10 carbon atoms, and Z′ is a branched chain alkyl, alkylene oralkylene oxide species having from about 12 to about 500 carbon atoms,or mixtures thereof.
 12. A thermosetting resin composition in accordancewith claim 10 wherein Y is a polyvalent radical selected from: branchedchain alkylene or alkylene oxide species having from about 12 to about500 carbon atoms, aromatic groups having the structure:

wherein n=1, 2 or 3, each Ar is a monosubstituted, disubstituted ortrisubstituted aromatic or heteroaromatic ring having in the range of 3up to 10 carbon atoms, and Z″ is a branched chain alkylene or alkyleneoxide species having from about 12 to about 500 carbon atoms, ormixtures thereof.
 13. A thermosetting resin composition according toclaim 12 wherein Q is —C(O)—O—.
 14. A thermosetting resin compositionaccording to claim 10 wherein X′ is derived from a dimer amine, andincludes —(CH₂)₉—CH(C₈H₁₇)—CH(C₈H₁₇)—(CH₂)₉—.
 15. A thermosetting resincomposition according to claim 10 wherein Y is selected from stearyl,behenyl, eicosyl, isoeicosyl, as well as: —O—[(CH₂)₂—O—]₄—,—(CH₂)₄—O—(C₃N₃)—[O—(CH₂)₄]₂—, wherein —(C₃N₃)— is a2,4,6-trisubstituted 1,3,5-triazine;

wherein —Ar— is a 1,3-disubstituted phenyl ring; Y is derived from adimer amine, and includes —(CH₂)₉—CH(C₈H₁₇)—CH(C₈H₁₇)—(CH₂)₉—;optionally hydrogenated α,ω-disubstituted polybutadienes, optionallyhydrogenated α,ω-disubstituted polyisoprenes, optionally hydrogenatedα,ω-disubstituted poly[(1-ethyl)-1,2-ethane].
 16. A thermosetting resincomposition according to claim 11 wherein X′ and Y are not botharomatic.
 17. A thermosetting resin composition according to claim 9,wherein the free radical initiator is selected from peroxides or azocompounds.
 18. A thermosetting resin composition according to claim 10wherein the coupling agent is selected from silicate esters, metalacrylate salts, titanates or compounds containing a co-polymerizablegroup and a chelating ligand.
 19. A polyvinyl composition having thestructure:

wherein: q is 1, 2 or 3, each R is independently selected from hydrogenor lower alkyl, Q is —C(O)—O—, and Y is selected from: branched chainalkylene or alkylene oxide species having from about 12 to about 500carbon atoms, aromatic groups having the structure:

wherein n=1, 2 or 3, each Ar is a monosubstituted, disubstituted ortrisubstituted aromatic or heteroaromatic ring having in the range of 3up to 10 carbon atoms, and Z is a branched chain alkylene or alkyleneoxide species having from about 12 to about 500 carbon atoms, ormixtures thereof.
 20. A thermosetting resin composition comprising (a) adivinyl composition according to claim 19, and (b) a, sufficient amountof at least one free radical initiator.
 21. The thermosetting resincomposition in accordance with claim 20, further comprising (c) asufficient amount of at least one coupling agent, based on the totalweight of the composition.
 22. The thermosetting resin composition inaccordance with claim 20, wherein the free radical initiator is selectedfrom peroxides or azo compounds.
 23. The thermosetting resin compositionin accordance with claim 21, wherein the coupling agent is selected fromsilicate esters, metal acrylate salts, titanates or compounds containinga copolymerizable group and a chelating ligand.
 24. An assemblycomprising a first article permanently adhered to a second article by acured aliquot of the thermosetting resin composition according to claim3.
 25. An assembly comprising a first article permanently adhered to asecond article by a cured aliquot of the thermosetting resin compositionaccording to claim
 10. 26. An assembly comprising a first articlepermanently adhered to a second article by a cured aliquot of thethermosetting resin composition according to claim
 19. 27. A die-attachpaste comprising: in the range of about 10 up to 80 wt % of thethermosetting resin composition according to claim 3, and in the rangeof about 20 up to 90 wt % of a conductive filler.
 28. A die-attach pastecomprising: in the range of about 10 up to 80 wt % of the thermosettingresin composition according to claim 10, and in the range of about 20 upto 90 wt % of a conductive filler.
 29. A die-attach paste comprising: inthe range of about 10 up to 80 wt % of the thermosetting resincomposition according to claim 19, and in the range of about 20 up to 90wt % of a conductive filler.
 30. A die-attach paste according to claim27 wherein the conductive filler is electrically conductive.
 31. Adie-attach paste according to claim 28 wherein the conductive filler iselectrically conductive.
 32. A die-attach paste according to claim 29wherein the conductive filler is electrically conductive.
 33. Adie-attach paste according to claim 27 wherein said conductive filler isthermally conductive.
 34. A die-attach paste according to claim 28wherein said conductive filler is thermally conductive.
 35. A die-attachpaste according to claim 29 wherein said conductive filler is thermallyconductive.
 36. An assembly comprising a microelectronic devicepermanently adhered to a substrate by a cured aliquot of the die attachpaste according to claim
 27. 37. An assembly comprising amicroelectronic device permanently adhered to a substrate by a curedaliquot of the die attach paste according to claim
 28. 38. An assemblycomprising a microelectronic device permanently adhered to a substrateby a cured aliquot of the die attach paste according to claim
 29. 39. Amethod for adhesively attaching a first article to a second article,said method comprising: (a) applying composition according to claim 27to said first article, (b) bringing said first and second article intointimate contact to form an assembly wherein said first article and saidsecond article are separated only by the adhesive composition applied instep (a), and thereafter, (c) subjecting said assembly to conditionssuitable to cure said adhesive composition.
 40. A method for adhesivelyattaching a first article to a second article, said method comprising:(a) applying composition according to claim 28 to said first article,(b) bringing said first and second article into intimate contact to forman assembly wherein said first article and said second article areseparated only by the adhesive composition applied in step (a), andthereafter, (c) subjecting said assembly to conditions suitable to curesaid adhesive composition.
 41. A method for adhesively attaching a firstarticle to a second article, said method comprising: (a) applyingcomposition according to claim 29 to said first article, (b) bringingsaid first and second article into intimate contact to form an assemblywherein said first article and said second article are separated only bythe adhesive composition applied in step (a), and thereafter, (c)subjecting said assembly to conditions suitable to cure said adhesivecomposition.
 42. A method for adhesively attaching a microelectronicdevice to a substrate, said method comprising: (a) applying die attachpaste according to claim 27 to said substrate and/or saidmicroelectronic device, (b) bringing said substrate and said device intointimate contact to form an assembly wherein said substrate and saiddevice are separated only by the die attach composition applied in step(a), and thereafter, (c) subjecting said assembly to conditions suitableto cure said die attach composition.
 43. A method for adhesivelyattaching a microelectronic device to a substrate, said methodcomprising: (a) applying die attach paste according to claim 28 to saidsubstrate and/or said microelectronic device, (b) bringing saidsubstrate and said device into intimate contact to form an assemblywherein said substrate and said device are separated only by the dieattach composition applied in step (a), and thereafter, (c) subjectingsaid assembly to conditions suitable to cure said die attachcomposition.
 44. A method for adhesively attaching a microelectronicdevice to a substrate, said method comprising: (a) applying die attachpaste according to claim 29 to said substrate and/or saidmicroelectronic device, (b) bringing said substrate and said device intointimate contact to form an assembly wherein said substrate and saiddevice are separated only by the die attach composition applied in step(a), and thereafter, (c) subjecting said assembly to conditions suitableto cure said die attach composition.
 45. Method for the preparation ofbismaleimides from diamines, said method comprising: adding diamine to asolution of maleic anhydride, adding acetic anhydride to said solutiononce diamine addition is complete, and then allowing the resultingmixture to stir for at least 12 hours, and thereafter treating theresulting reaction mixture with a suitable isomerizing agent.